For the purpose of filling containers to a constant level with a still liquid, filling nozzles are previously disclosed comprising an annular connection part configured to provide a liquid-tight support with a neck of a container and to demarcate a distribution zone; a distribution tube connected to a source of supply of a liquid under a distribution pressure by means of a distribution valve and discharging into the distribution zone; an exhaust duct discharging on the one hand into the distribution zone, and on the other hand via a vent orifice, and an exhaust check valve controlled by a liquid level sensor inside the exhaust duct, interposed in the exhaust duct between the distribution zone and the vent orifice. When filling a container, the air that is present inside the container is expelled by the liquid as it is introduced into the container and escapes via the vent orifice. When the liquid reaches the lower extremity of the exhaust duct, the liquid rises in the exhaust duct and causes the closure of the exhaust check valve. The distribution valve is then closed, and the container is separated from the annular connection part in such a way that the liquid that is present inside the exhaust duct returns into the container.
These filling nozzles cannot be used for the packaging of sparkling liquids, that is to say liquids containing a gas dissolved in the liquid, because of the de-gassing which occurs at the time of the introduction of the liquid into the container.
Also familiar, in particular from the document U.S. Pat. No. 3,946,770, and from the document U.S. Pat. No. 4,206,789, are devices comprising a highly complex system of tubes and valves positioning the filling nozzle in relation to a pressure vessel containing the liquid to be packaged in such a way as to place the supply vessel and the container under the same pressure. During filling, the air that is initially present inside the container is returned to the supply vessel and thus risks causing pollution of the liquid to be packaged. Furthermore, it is difficult to perform effective cleaning because of the complexity of the circuits.